1. Field of the Invention
The invention relates to a pile hammer comprising a cylinder, a piston displaceably guided in the cylinder, and a striker displaceably guided in the cylinder.
2. Description of the Related Art
Such pile hammers, which are regularly also called diesel hammers or diesel pile drivers, are particularly used in foundation work in the construction industry. The pile hammers are used for driving posts of all kinds, such as concrete pillars, iron beams, sheet pile wall elements or the like into a construction ground.
To start such a pile hammer, the piston is pulled upward using a disengagement apparatus, and released at a specific height, thereupon dropping downward under the effect of gravity. As it drops, the piston activates a fuel pump, by way of which fuel, particularly diesel oil, is supplied to one or more injection nozzles, which inject the fuel into the combustion chamber of the cylinder. The air situated in the combustion chamber of the cylinder is compressed as the piston drops, and thereby heated so that the fuel/air mixture present in the working chamber is ignited, whereupon it combusts in the manner of an explosion. The explosion energy released during this process accelerates the piston back upward for a new work cycle, on the one hand; on the other hand, the material being pile-driven is driven into the ground.
When the piston is catapulted upward, it exits from the cylinder, which is open at the top, with its end during regular operation, before sliding downward again. Because of incomplete combustion in connection with disadvantageous ground properties, however, it cannot be precluded that such excessive energy acts on the piston during the explosion of the diesel/air mixture that the piston is catapulted completely out of the cylinder. This situation results in a significant hazard potential.